A challenge in modern drug therapy is to develop strategies for safer and more selective targeting of drug delivery in pregnancy. Specifically, approaches are needed that would restrict unnecessary drug exposure to either mother or fetus. There is evidence emerging that indicates the placenta does express natural transport and metabolism processes that function to control drug and nutrient distribution between the mother and fetus. Further, in vitro techniques developed in the past 10 years now provide some of the tools necessary to elucidate transport and metabolism processes typical of the human placenta. As a consequence, pharmaceutical scientists are in a position to contribute significantly to the design and development of drugs for pregnancy.